24. Phurnacite briquettes, manufactured by Coal Products Limited at Immingham Briquetting Works, Immingham, Humberside, which—
(a)comprise anthracite duff (as to approximately 65 per cent. to 85 per cent. of the total weight), Petroleum Coke (up to approximately 20 per cent. of the total weight) and molasses and phosphoric acid as binder (as to the remaining weight);
(b)were manufactured from those constituents by a process involving roll-pressing and heat treatment at about 300°C;
(c)are ovoid-shaped briquettes with two parallel indented lines running longitudinally around the briquette and have an average weight of 40 grammes; and
(d)have a sulphur content not exceeding 1£5 per cent. of the total weight.